1.AdjectiveDecisively beaten; defeated; rendered irrelevant for the long term.
"As the company grew, one after another of its smaller competitors ended up down for the count."
2.AdjectiveSoundly unconscious, either because asleep or because otherwise knocked out.
"A: Look at him, he's out like a light! B: Yeah, he had a long day! And now he's down for the count."
3.AdjectiveUsed other than figuratively or idiomatically: see down, for, the, count: lying upon the mat of a boxing ring while the referee counts the fighter out.
"Liston was down for the count more than once before rising up to regain command of the fight."